A carbon nanotube has a cylinder-shaped structure in a nanometer unit, wherein carbon atoms are arranged in a spiral form. With this structure, the carbon nanotube has its unique physical properties that are not observed in a general material. With regard to such a carbon nanotube, various application technologies have been developed using the excellent physical properties of the carbon nanotube, e.g., its unique electrical property, intensity, a restoration property, and thermal conductivity.
However, in case of single-walled carbon nanotubes, all constitutional atoms thereof are surface atoms. Accordingly, the carbon nanotubes are easily aggregated by a van der Waals force. Most single-walled carbon nanotubes are formed in a structure of a bundle or an aggregate consisting of a multiple number of carbon nanotubes. Multi-walled carbon nanotubes also are in the state of being entangled with one another like a net thereby forming a large aggregate.
Chemical and physical operations of the aggregate of carbon nanotubes are difficult. And also the aggregation of carbon nanotubes has been a serious obstacle to the industrial application of the carbon nanotubes. Under the circumstances, the necessity to develop a technology relating to a method for dispersing a carbon nanotube aggregate is increasing.
With respect to a conventional method for dispersing a carbon nanotube in a solution, there has been proposed a physical dispersion treatment method such as an ultrasonic wave treatment. As to a specific example of the method for dispersing a carbon nanotube, there has been known a method of putting a single-walled carbon nanotube aggregate in acetone and dispersing the carbon nanotubes therein through an ultrasonic wave treatment.
In addition to the ultrasonic wave treatment, there has been proposed a method of increasing compatibility to a solvent of a carbon nanotube by adding a surfactant or other materials to a solvent.
However, in the conventional method for dispersing a carbon nanotube, an effect in dispersion of a carbon nanotube is not remarkable. Further, an external damage to a carbon nanotube may occur. Thus, development of a method for easily dispersing a carbon nanotube without damaging the carbon nanotube has been demanded.